The invention relates to a puncturing system for generating a puncture wound for obtaining a sample of a body fluid. The body fluid is typically blood, but in some cases may be interstitial fluid. Reference shall be made hereinafter to blood as an example of body fluids, recognizing that fluids other than blood can be obtained from a puncture wound.
Puncturing systems (lancing devices) of this type usually consist of disposable puncturing elements that are designed for single use for puncturing the skin and a puncturing device having a drive for the puncturing motion of the puncturing element. The puncturing device of a puncturing system of this type has a press-on part to be pressed onto the body part in which a puncture wound is to be generated and a triggering means, by the actuation of which a user can trigger a puncturing motion of a puncturing element.
It is a consistent goal in the development of puncturing systems to generate with as little pain as possible a puncture wound from which a useful sample, i.e., a sufficient quantity of a body fluid, can be obtained. The depth of penetration is very important for both the sensation of pain and for obtaining the sample. In general, both the sensation of pain as well as the quantity of liquid that can be obtained from the puncture wound increase with increasing depth of puncturing. Puncturing devices are therefore required, on the one hand, to keep the depth of puncturing as small as possible, while on the other hand providing it to be as deep as necessary.
An important test parameter in this context is the pressure at which the press-on part is pressed onto a body part. If the pressure is too low, it is possible that the desired depth of puncturing will not be reached during a puncture and that a useful sample will not be obtained for this reason. In this case, the puncturing procedure must be repeated, which is extremely unpleasant for a user.
In order to reduce the likelihood of an unsuccessful puncture, it is known to provide a puncturing device having a pressure sensor, in which a puncturing motion is triggered automatically as soon as a pressure that exceeds a predetermined minimum pressure bears on the press-on part. Such devices are known, for example, from U.S. Pat. No. 5,879,311.
A puncturing device having a built-in pressure sensor is also described in EP 1 360 933. However, a puncture is not triggered automatically by the pressure sensor in this puncturing device. Instead, the device only displays whether the pressure bearing on the press-on part is within one of three predetermined ranges (low, normal, and high). A puncturing motion is triggered by pressing a key on the device housing.
A puncturing device having a built-in pressure sensor is also known from EP 1 407 712. In this device, a negative pressure is generated after the device is placed against the skin such that the tissue is made to bulge into a device opening. The negative pressure generated is measured with the pressure sensor and compared to a stored threshold value. In this context, EP 1 407 712 mentions both the possibility of a puncturing motion being triggered automatically as soon as the negative pressure reaches a favorable value, as well as the possibility of a puncture being triggered by a user by closing a switch when it is displayed that the measured negative pressure has reached a predetermined threshold value.
It is desirable to devise a way in which the risk of an unsuccessful puncture that fails to obtain a useful sample can be reduced while at the same time keeping the convenience for the user as high as possible without increasing the sensation of pain due to the depth of puncturing being unnecessarily large.